This issue was fixed in the openstack/nova 16.1.5 release.
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https://bugs.launchpad.net/bugs/1739646
Title:
Instance type with disk set to 0 can cause DoS
Status in OpenStack Compute (nova):
Fix Released
Status in OpenStack Compute (nova) ocata series:
Fix Committed
Status in OpenStack Compute (nova) pike series:
Fix Committed
Status in OpenStack Compute (nova) queens series:
Fix Committed
Status in OpenStack Security Advisory:
Won't Fix
Status in OpenStack Security Notes:
New
Bug description:
In OpenStack at the moment, there is the ability to create instance
types with disk size 0. The API documentation states the following:
"The size of the root disk that will be created in GiB. If 0 the root
disk will be set to exactly the size of the image used to deploy the
instance. However, in this case filter scheduler cannot select the
compute host based on the virtual image size. Therefore, 0 should only
be used for volume booted instances or for testing purposes."
In a cloud environment where a deployer wants to offer boot-from-
volume instances, those instance types will be there. However, this
means that a user can upload an image of 4TB and boot small instances
where each one will have 4TB of storage, potentially exhausting the
disks local storage (or Ceph cluster if using Ceph for ephemeral
storage).
I'm not sure if this is a security issue or it should be published as
an advisory, but I believe there should be an option to disable the
feature of booting an instance with the exact size of the image used
so deployers have the ability/choice to provide boot-from-volume
instance types.
I can confirm this in our environment that if a customer creates an
instance with 200GB of ephemeral disk space, they can take an image of
it, then create an instance with that image on an instance type that
has no ephemeral disk space and get 200GB of disk.
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